1. Field of the Invention
The present invention relates to a viewing angle controlling system, and an image display device using the same.
2. Description of the Related Art
Image display devices, such as liquid crystal displays (LCD), plasma display devices (PDP) and EL display devices (ELD), are used for various purposes and scenes since the display devices have advantageous characteristics that: the display devices may be thin and light; the power consumption thereof is low; the screen thereof can be made large and the like. In particular, LCDs or ELDs are widely used as display devices of personally-used information devices, such as notebook computers or cellular phones. In some cases, such an information device is used to handle data including personal data, trade secrets or the like. However, the device has such a risk that its screen is peeped by others on a platform of a station, or in a public facility such as a coffee shop or on a train so that privacy is invaded, confidential information leaks out, or the like. Further, in the same case as in an automatic teller machine (ATM) or others, there would be a risk that a personal identification number or the like is peeped when the machine is operated, so that information leaks out. In the meantime, in the case of displays adapted for cars, such as a car navigation system, there is caused a problem that light emitted upwards from the display is projected on the front window, in particular, in driving at night so that the visual field of the outside may be shut out.
It is stated that out of the above-mentioned image display devices, LCDs are “narrow in viewing angle” in comparison with selfluminous-type display devices such as CRTs, ELDs and PDPs. In order to enlarge the viewing angle thereof, compensation films are used. In such a case, the wording “narrow in viewing angle” precisely means that “the viewing angle at which a good display property is exhibited is narrow”. In other words, even in a display device which is generally said to be “narrow in viewing angle”, light for display information is emitted in every direction; thus, there remains a possibility that information is read out by peep or the like of other persons, and the problems of the projection of the light and the like are not solved. From such a viewpoint, it is necessary to control the quantity of light emitted from the image devices in accordance with the emission angle thereof, thereby decreasing the light emission into an unnecessary direction or into a direction along which the light quantity is desired to be limited into an extent that information based on the light cannot be read out.
Against such a problem, a film in which louvers are physically formed in the form of a bamboo blind, or the like is used between protective films such as PET films (see, for example, JP-A-2001-305312). Such a film is also called a light control film or the like, and is already commercially available. The film in which louvers are formed, is, for example, a film as illustrated in FIG. 2, wherein a large number of light-absorbable louvers 202 are fitted to protective films 203 at a right angle or a predetermined angle. By adjusting the height of the louvers 202, the arrangement interval between the louvers 202 and a translucent layer 201, or the arrangement angle between the louvers 202 and the protective films 203, or by laminating a plurality of such structure units 200 onto each other, various viewing-angle-controls can be attained.
As disclosed in JP-A-2001-305312, such a louver film is produced by a method of laminating transparent layers, which will be translucent regions, and colored layers, which will be louver regions, alternately so as to have a required size; slicing the resultant; and then laminating protective films onto two surfaces thereof. For this reason, considerably complicated steps are required for the production, thereby causing problems that cost of a louver film increases and the design for viewing-angle-control is lacking in flexibility. Additionally, the number of the lamination of transparent layers and colored layers is restricted, so that the lamination thickness becomes a factor for deciding the size of the louver film. Thus, the area thereof is not easily made large.